1. Field of the Invention
The present invention relates to compression-release brake systems for internal combustion engines in general, and, more particularly, to a self-contained compression-release brake control module for a compression-release engine brake system of an internal combustion engine.
2. Description of the Prior Art
For internal combustion engines (IC engine), especially diesel engines of large trucks, engine braking is an important feature for enhanced vehicle safety. Consequently, the diesel engines in vehicles, particularly large trucks, are commonly equipped with compression-release engine brake systems (or compression-release retarders) for retarding the engine (thus, vehicle). The compression release engine braking provides significant braking power in a braking mode of operation. For this reason, the compression-release engine brake systems have been in North America since the 1960's.
The typical compression-release engine brake systems open exhaust valve(s) just prior to Top Dead Center (TDC) at the end of a compression stroke, which is a standard technology for a compression-release engine braking. This creates a blow-down of the compressed cylinder gas and the energy used for compression is not reclaimed. The result is engine braking, or retarding, power. A conventional compression-release engine brake system has substantial cost associated with the hardware required to open the exhaust valve(s) against the extremely high load of a compressed cylinder charge. Valve train components must be designed and manufactured to operate reliably at high mechanical loading. Also, the sudden release of the highly compressed gas comes with a high level of noise. In some areas, engine brake use is not permitted because the existing compression-release engine brake systems open the valves quickly at high compression pressure near the TDC compression that produces high engine valve train loads and a loud sound, which has resulted in prohibition of engine compression release brake usage in certain urban areas.
Typically, the compression-release engine brake systems up to this time are unique and custom designed and engineered to a particular engine make. The design, prototype fabrication, bench testing, engine testing and field testing typically require twenty four (24) months to complete prior to sales release. Accordingly, both the development time and cost have been an area of concern.
Exhaust brake systems can be used on engines where compression release loading is too great for the valve train. The exhaust brake mechanism consists of a restrictor element mounted in the exhaust system. When this restrictor is closed, backpressure resists the exit of gases during the exhaust cycle and provides a braking function. This system provides less braking power than a compression release engine brake, but also at less cost. As with a compression release brake, the retarding power of an exhaust brake falls off sharply as engine speed decreases. This happens because the restriction is optimized to generate maximum allowable backpressure at rated engine speed. The restriction is simply insufficient to be effective at the lower engine speeds.
While known compression-release engine brake systems have proven to be acceptable for various vehicular driveline applications, such devices are nevertheless susceptible to improvements that may enhance their performance and cost. With this in mind, a need exists to develop improved compression-release engine brake systems that advance the art, such as a self-contained compression brake control module for a compression-release brake system of an internal combustion engine that significantly reduces the development time and cost of the compression-release engine brake system and enhances performance thereof.